1. Field of the Invention
The present invention relates generally to electric power systems and more specifically to a variable reluctance electric power system which may be used as an alternator, a motor, or in combination.
2. Background Information
In the United States and throughout the world, millions of people use electric motors and alternators on a daily basis. Conventional motors and alternators have a variety of configurations, but ordinarily consist of a metal case (usually steel), a stator which is secured inside the case, and a rotor which turns on bearings mounted at the ends of the case. There are other electric motor configurations, but a great majority have this configuration. A stator usually includes a series of laminations with interior windings, usually of copper wire. The laminations are insulated from each other, are stacked, and are configured so as to hold the stator windings within the interior of the stator. Rotors have many configurations, but often have windings, laminations, magnets, commutators, or slip rings.
Electric motors may be either alternating current (a-c) or direct current (d-c) motors. In a-c motors, the stator can be wound with either single or multiple phase windings. The most common a-c motors are three phase with the windings interspersed and displaced 120 electrical degrees from each other. The basic design of the most common a-c motor in use today, the induction motor, has been known since the late 1800's and it is still considered by many to be the most economical to build for any given horsepower. In spite of its popularity, the induction motor has several serious drawbacks including: its starting torque is very low, it requires six to eight times its rated full load current to start, and speed control is difficult and requires considerable auxiliary equipment to be accomplished effectively. In addition, induction motors most often have a rotor generally consisting of stacked laminations in which several generally shorted aluminum windings are embedded.
Common d-c motors are more desirable for many applications than a-c induction motors, because they have a much higher starting torque and do not require the high starting current. However, the rotor in these d-c motors must have windings, commutation bars, and brushes to conduct the rotor current. This rotor configuration makes them expensive to manufacture, expensive to maintain, and limits the speed at which the rotor can turn and keep the windings safely embedded. Some d-c rotors have embedded magnets which reduces or eliminates some of these problems, but there is some degradation of performance.
For a variety of well established reasons, standard electric power operates at a frequency of 50 or 60 Hz. Because of their necessary configurations, the fastest conventional alternators can run for generating conventional electric power is 3,600 rpm at 60 Hz and 3,000 rpm for 50 Hz. If a device such as a modern turbine which may easily operate a speeds of around 50,000 rpm's are used to power such alternators, the speed must be mechanically reduced to either 3,600 rpm or 3,000 rpm to function properly. Furthermore, the operating speed of the turbine must be rigidly controlled for proper operation.
The variable reluctance electric power system of the instant invention solves a number of problems common to conventional motors and alternators and may be constructed either in a motor configuration or an alternator configuration. The rotor of the instant invention is solid and does not include windings, brushes, commutators, slip rings, laminations, or embedded magnets such as in more conventional a-c or d-c motors. For lower speed applications, the rotor may have the configuration of a hollow squirrel cage. A high speed drive device such as a turbine may be used without the necessity of using mechanical speed reduction in the alternator configuration. Even though the motor configuration is, basically, an a-c motor, it does not require the high start up current of a conventional a-c motor. Further the instant invention provides high starting torque. That is, the instant invention provides the benefits of both conventional a-c and d-c motors without having their inherent drawbacks.
The ideal variable reluctance electric power system should operate with a solid rotor having no windings, brushes, commutators, slip rings, laminations, or embedded magnets. The ideal variable reluctance electric power system may also provide for a rotor having a hollow, squirrel cage type configuration for lower speed operation, also without the need for windings, brushes, commutators, slip rings, laminations, or embedded magnets. The ideal variable reluctance electric power system in the alternator configuration should provide for the use of a high speed power source such as a turbine without the need for mechanical speed reduction. The ideal variable reluctance electric power system in the motor configuration should eliminate the high startup current requirement of conventional a-c electric motors. The ideal variable reluctance electric power system in the motor configuration should also provide high starting torque. The ideal variable reluctance electric power system should also be simple, reliable, inexpensive, and easy to operate and maintain.